The present invention relates to a light irradiation control device for use in an image recording apparatus. More particularly, this invention relates to a device for controlling light irradiation againt an original or an image recording medium in response to thickness and material of the original or an intermediate masking member for use in the image recording apparatus.
In a conventional color image recording apparatus, a photosensitive recording medium is properly exposed to light through an intermediate mask member on which a mask image is provided. This light exposure is provided irrespecitive of the light transmission factor of the mask member.
Further, a color image recording apparatus using such mask member is proposed in a commonly assigned copending U.S. patent application Ser. No. 184,576 filed on Apr. 21, 1988. According to this apparatus, used is a transfer type image recording mediums disclosed in U.S. Pat. No. 4,399,209. Each of the mask members carrying an image corresponding to three colors outputted from a monochroprinter is brought in intimate contact with a photosensitive pressure-sensitive recording medium, and then the photosensitive pressure-sensitive recording medium is exposed to light through the mask member, thereby forming a color latent image on the recording medium. Subsequently, a separate image recording medium such as a developer sheet is placed on the photosensitive pressure sensitive recording medium, and these recording mediums are pressed together by a pressure developing unit. As a result, a color image is formed on the developer sheet.
According to the image recording apparatus disclosed in the copending application, the light transmission factor of the mask member have to be constant at all times for providing a desirable output image on the developer sheet. If used is a different type of the mask member having the light transmission factor different from that of the oridinary mask member, it is necessary to manually readjust the light irradiation intensity or light irradiation time. Such adjustment may be intriate and troublesome.
In another aspect, in the conventional image recording apparatus, an original is placed on an original support stand, end light is irradiated onto the original so as to provide a latent image on a photosensitive recording medium. In the conventional apparatus, light amount or intensity is normally kept constant irrespective of thickness of the original. However, since the light is transmitted through the original, and such transmitted light is introduced to an exposure unit for exposing the photosensitive recording medium to light, the quality of the output image may be changeable in response to the thickness of the original. For example, only a limit amount of light may be transmitted through the origianl if the original has a large thickness, thus deteriorating the quality of the output image.